0

Experimentally, the universe keeps expanding. I do not understand well what is meant by expanding universe.

If we assume an inertial reference frame for which space is defined and if in this reference frame we define a proper length as the distance between 2 atoms in the $O_2$ molecule(both atoms belong to the same inertial reference frame). My question is :

Since the universe is expanding, is that distance going to increase with universe expansion or could that distance be used to measure that universe has indeed expanded?

I feel there is some picture that I have got wrong.

Ronan Tarik Drevon
  • 769
  • 3
  • 15
  • Are you asking whether the $O_2$ bond length increases as the universe expands? If so see Why does space expansion not expand matter? – John Rennie Aug 29 '17 at 14:56
  • Well, you have the scale wrong, (or I have your question wrong,sorry), that particular measuring device is far too short to measure expansion of space. The electrostatic attraction is much greater than any stretch of space will overcome, –  Aug 29 '17 at 15:00
  • @countt010 that was a mind experience not a realistic one but we could have taken the measuring system earth-moon whose relative motions are slow enough to consider them as belonging to the same inertial frame. However, they experience acceleration which means they are not inertial frame... – Ronan Tarik Drevon Aug 29 '17 at 15:02

0 Answers0